Method for granulating polymers and product produced by this method

Abstract

A granulation method that can be used to obtain a polymer from post-consumer materials, and a motor vehicle part made from polymers produced by recycling used polymers.

Claims

1. A method for granulating polymers from ground post-consumer materials, wherein said method comprises a step of: extracting dissolved salts and/or small unmelted clusters present within said polymers; wherein said extracting step comprises the step of adding a fluid or mixture of fluids in an extruder which solubilizes said dissolved salts and/or small unmelted clusters or entrains them, at least one of said dissolved salts and/or small unmelted clusters so extracted being evacuated under atmospheric pressure or under vacuum during extrusion before passing into an extrusion head; wherein said fluid is at least one of water or a mixture containing water, introduced into said extruder at a pressure greater than that present in said extruder; wherein 60 g of water or more is added per kg of extruded material; and wherein said method further comprises a step of granulating said polymers after passing through a die of said extrusion head; wherein said method is used to extrude a polymer that is used for molding a part, that, after coating, has a maximum in the appearance areas of visible parts of 4 faults of type grains, craters, or particles, per m.sup.2, of size greater than 50 m.

2. The method for granulating according to claim 1, wherein said fluid is a mixture comprising at least one of liquid carbon dioxide, liquid nitrogen, acetone, alcohol.

3. The method for granulating according to claim 1, wherein said fluid or said mixture of fluids is added last, including after any additives.

4. The method for granulating according to claim 3, said fluid or said mixture of fluids being added in the second half of the length of the extruder, about two thirds of the way along said extruder.

5. The method for granulating according to claim 1, wherein said polymers to be granulated are polyolefins, which are chosen from homopolymers or copolymers of olefins.

6. The method for granulating according to claim 2, wherein said fluid or said mixture of fluids is added last, including after any additives.

7. The method for granulating according to claim 3, wherein said polymers to be granulated are polyolefins which are chosen from homopolymers or copolymers of olefins.

8. The method for granulating according to claim 2, wherein said polymers to be granulated are polyolefins which are chosen from homopolymers or copolymers of olefins.

9. The method for granulating according to claim 2, wherein the alcohol is selected from methanol, ethanol and butanol.

10. The method for granulating according to claim 5, wherein said polyolefin is polypropylene.

11. The method for granulating according to claim 7, wherein said polyolefin is polypropylene.

12. The method for granulating according to claim 8, wherein said polyolefin is polypropylene.

Description

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

(1) The invention will be better understood on reading the description which follows, given purely by way of non-limiting example and with reference to the drawings wherein:

(2) FIG. 1 is a schematic representation of a device according to the invention;

(3) FIG. 2 is a front view in perspective of a front bumper of a motor vehicle;

(4) FIG. 3 is a front view in perspective of a front bumper of a motor vehicle; and

(5) FIG. 4 is a front view in perspective of a rear bumper of a motor vehicle.

(6) FIGS. 5 to 7 are representations of appearance faults:

(7) FIG. 5 is an enlarged sectional view of a crater type fault;

(8) FIG. 6 is an enlarged sectional view of a particle type fault; and

(9) FIG. 7 is an enlarged sectional view of a grain type fault.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(10) FIG. 1 shows an extrusion device according to the invention, designated by the general reference 10. The features and method of the invention described earlier are incorporated herein.

(11) The device 10 forms an extruder and comprises a stator 12 forming a barrel 14 and a rotor 16 forming a worm screw 18 (single or twin screw) system. The screw 18 is rotatable in the barrel 14. The barrel 14 and the screw 18 define an annular space 19 in which a composition to be extruded is driven forward.

(12) The device 10 comprises a main upstream inlet 20 adapted for the introduction of compounds, in this case the ground materials and possibly some additives conventionally added during extrusion, such as oxidants. The device 10 comprises a hopper 22 for the introduction of ground materials and additives in the main upstream inlet 20. The device 10 also comprises an outlet 31 provided with an extrusion head 24 equipped with a die 33.

(13) The device 10 comprises a first intermediate inlet 26 arranged just downstream from the main upstream inlet 20. The first intermediate inlet 26 is adapted for the introduction of an additive.

(14) The device 10 also comprises a second intermediate inlet 28 arranged downstream from the main upstream inlet 20 and from the main intermediate inlet 26. The second intermediate inlet 28 is adapted for the introduction of pressurized water.

(15) Lastly, the device 10 comprises an outlet 32 leading to a vacuum pump adapted to evacuate the mixture of water and pollutants extracted during extrusion.

(16) FIG. 2 is a perspective view of a front bumper 1 of a motor vehicle. Areas 2 and 3 correspond to the appearance areas of the bumper 1.

(17) FIG. 3 is a perspective view of a front bumper 4 of a motor vehicle. Areas 5 and 6 correspond to the appearance areas of the bumper 4.

(18) FIG. 4 is a perspective view of a rear bumper 7 of a motor vehicle. Areas 8 and 9 correspond to the appearance areas of the bumper 7.

(19) Areas 1 to 6 correspond to the appearance areas of the bumpers.

(20) FIG. 5 is a sectional view enlarged at a scale of 30:1 of an outer portion of a painted bodywork part 1 consisting of a substrate 2 and a paint film 3. The thickness of the paint film 3 varies between points B and C, where it is equal to 100 m. It is equal to 0 m at point A. In contrast, outside the segment [BC], the film thickness is constant. The portion of the paint film 3 located between points B and C, extending over a length of 0.6 mm, is a schematic representation of a crater type fault 4.

(21) FIG. 6 shows a sectional view enlarged at a scale of 30:1 of an outer portion of a painted bodywork part 1 consisting of a substrate 2 and a paint film 3. The substrate 2 of this figure, unlike that of FIG. 5, does not have a straight surface. Its surface appears to be convex in the portion extending from point D to point E located next to an impurity 5. The portion of the paint film 3 extending from point E to point F, over a length of 1.8 mm, is deformed. It is a schematic representation of a particle type fault 6.

(22) FIG. 7 shows a sectional view enlarged at a scale of 75:1 of an outer portion of a painted bodywork part 1 consisting of a substrate 2 and a paint film 3. The paint film has a constant thickness of 93 m. A dust particle 7 is deposited on the last coat of the paint film. This fault, extending from points F to G over a length of 0.2 mm, is a schematic representation of a grain type fault 8. The other causes of grain type faults, namely the presence of a dust particle on the substrate surface or between two successive coats of the paint film, creating an appearance fault by deformation of the paint film, are not shown.

(23) The method is not limited to the embodiments described above.

(24) Volatile organic compounds, dissolved salts and/or small unmelted clusters can in fact be extracted through the use of a fluid other than water or a mixture of fluids.

(25) Also, the granulation method can be used to manufacture parts other than bodywork parts for motor vehicles and even parts for sectors other than the automotive sector.

(26) Lastly, the granulation method can be applied to polymers other than polypropylene.

(27) While the process and method herein described constitute preferred embodiments of this invention, it is to be understood that the invention is not limited to this precise process and method, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.